1. Field of the Invention
The present invention pertains to hermetically sealed, positive displacement compressors for use in refrigeration systems such as air conditioners, refrigerators and the like, and methods for assembling such compressors.
2. Description of the Related Art
Various types of positive displacement compressors have been used in refrigeration systems including, for example, reciprocating piston, rotary vane, and scroll type compressors. In addition, multi-cylinder compressors, such as twin cylinder rotary compressors, are also known in the art. In general, twin cylinder rotary compressors comprise a housing containing a motor and a compression mechanism. The compression mechanism includes two cylinders, each defining a bore. The motor generally includes a crankshaft that extends through the two cylinders and has two eccentric portions, one located in the bore of each cylinder. The crankshaft is driven by the rotor of a motor having a stator which is connected to a power source via a terminal assembly. The motor rotates the crankshaft which, in turn, rotates the eccentric portions within the bores of the cylinders. Each eccentric portion has a roller piston rotatably mounted thereon, which revolves within the bore and cooperates with one or more sliding vanes and the cylinder wall to provide a pumping action for compressing a refrigerant within the cylinder bore.
Terminal assemblies, as described above, provide power to the stator. Prior terminal assemblies, generally, include a terminal body and a plurality of conductor pins. The terminal body is typically cup-shaped and is mounted in an aperture within the wall of the compressor housing. The terminal body has a plurality of holes each defined by a collar or annular lip. The conductor pins extend through and are secured within the holes by the annular lip and an insulating glass seal, which electrically insulates the pins from the terminal body. The interior ends of the conductor pins are connected to lead wires running to the stator and the exterior ends of the conductor pins are connected to a source of electrical power.
In order to prevent refrigerant leakage and accommodate the high pressures within the compressor, parts of the compressor are machined to extremely close tolerances and the compressor housing is hermetically sealed. In the case of the terminal assembly, the terminal body of the assembly is tightly fitted within an aperture of the compressor housing and is then sealed to the wall of the housing, typically by welding, brazing or the like. Ideally, terminal assemblies are assembled prior to mounting and welding the terminal body to the housing. However, the cup-shaped terminal body of prior terminal assemblies are often unable to withstand the high heat of welding or brazing. Consequently, the subsequent welding of the pre-assembled terminal assembly to the housing often results in damage to the terminal body, insulators and/or the conductive pins. In addition, the interior of compressors using carbon dioxide as a working fluid reaches substantially high temperatures and pressures. Prior terminal assemblies, particularly the mounting of the conductive pins within the holes of the terminal body, are often unable to withstand the high pressures created in these compressors. Therefore, a need remains for a terminal assembly that can better endure the welding process by which the terminal assembly is fixed to the compressor housing and is better able to withstand the higher pressures and temperatures experienced in a hermetic compressor using carbon dioxide as the refrigerant.
In addition, prior compressors often required extensive machining of the housing and the housing aperture to achieve a tight fit between the terminal body and the aperture of the housing. Such extensive machining adds difficulty, time and expense to the assembly process. Therefore a need remains for a terminal assembly that can be installed on the housing without the need for extensive machining of the housing.